The invention relates to a device for dispensing viscous materials such as toothpaste, syrups, caulks, and the like. More particularly, the invention relates to an advancing piston dispenser.
Viscous materials have special dispensing problems due to their inherent properties. They cannot be poured from a container, nor can they be handled directly. Generally the only way to dispense a viscous material is to squeeze or push it out of a container.
The most common method of dispensing a viscous material is by squeezing a container enclosing the material. The material is forced out of an opening by the pressure of the container upon the material. Often this dispensing method is used with tube shaped containers that contain a variety of materials, including toothpaste. This method has a severe limitation, in that it is usually not possible to squeeze out all of the material from the container, and the remainder is always wasted. The consumer is faced with the dilemma of struggling to extract the remaining material, or needlessly wasting it. Further, it is difficult to simultaneously exert sufficient force upon the container the expel some of the material while careful controlling the dispensing. Thus, often either too little or too much material is dispensed. In addition, the material cannot be dispensed onto the precise desired location.
Another common method of dispensing viscous materials comprises an apparatus wherein viscous materials are forced out of a storage chamber by an advancing piston. Typically, the piston is advanced incrementally along a notched rod toward a discharge orifice. The piston may be continually advanced until it reaches the limit of its travel, which is typically near, but not at, the opening. In operating many of these types of devices, the operator must often grip component parts which are covered with the viscous material to be dispensed. The result is often slippage which lessens the quantity of material dispensed, or prevents completely the dispensing of any viscous material. In addition, since the piston is advanced incrementally, it is extremely difficult to control the quantity of material dispensed. The sudden surge of each notch realized can cause a large volume of material to leave the dispenser unexpectedly.
These problems are especially acute among the elderly, young children, people with arthritis and other people that have difficulty exerting sufficient force to expel the materials and sufficient motor ability to control the material's output. Since household materials, including toothpaste and syrup often must be dispensed by these groups of people, these dispensing methods are undesirable for such products.
U.S. Pat. No. 4,753,373 to Seager discloses a positive displacement dispenser comprised of numerous moving parts which dispenses material upon depression of an actuating lever drive bar assembly which turns a rotatable wheel, thus turning a threaded rod and drawing a piston towards a discharge orifice located along the outer edge of its housing.
U.S. Pat. No. 4,850,516 to Seager discloses a positive displacement dispenser comprised of numerous moving parts, which dispenses material upon depression of an actuating lever drive bar assembly which turns a rotatable wheel, thus turning a threaded rod and drawing a piston towards the discharge orifice. A one-way mechanism is also provided for, to prevent the piston from retracting within the chamber.
U.S. Pat. No. 4,506,810 to Goncalves discloses a dispensing device comprising a reciprocating rack assembly which, when activated by a manually operated push-button assembly, forces a piston through a cylinder towards a dispensing orifice opposite the pushbutton assembly.
U.S. Pat. No. 5,303,850 to Connan discloses a dispensing cap comprising a one piece cap having a dispensing outlet which is aligned with a dispensing outlet in the neck of a bottle upon rotation of the cap.
U.S. Pat. No. 5,305,932 to Iseli discloses a permanent, snap-on, twist open cap and dispenser.
U.S. Pat. No. 4,144,988 to Bergman discloses a twist top actuated dispenser wherein manual rotation of a twistable projection causes a piston to advance towards an opposite end, thus dispensing material from a fixed spout at that opposite end.
U.S. Pat. No. 4,964,548 to Kenyon Jr. discloses a dispensing closure having an interior sealing sleeve, a threaded sleeve engaging a threaded tube, and stop blocks limiting twisting of the closure cap.
While these units units may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present invention as disclosed hereafter.